Grubscrew removal - UK Vintage Radio Repair and Restoration Discussion Forum

MichaelR · 30th Jun 2009, 9:20 pm

Hi to those "in the know",

Could anybody offer Tips or hints as to how to remove grubscews that have been worn so that suitable allen keys cannot be used to turn them.

regards
Mike

AlanBeckett · 30th Jun 2009, 9:33 pm

Mike,
I've done the following, although it's a bit SorB:-
Choose the next size up - metric if the original is imperial, and vice versa.
Cut off a section of the key so you have a straight piece of hex.
Support the knob or whatever, line up the flats on the hex with the flats on the corpse as best you can and tap it in, hard.
Unscrew it.
I've tried it with brass rod filed up but it's not hard enough.
The ball-ended keys are best, but more expensive.
The secret is a good tight fit and hope. I assume you've already applied WD, heat etc.
Good luck.
Alan

Oldtimer74 · 30th Jun 2009, 11:53 pm

I assume you are talking about grub screws in knobs. If they are so worn that the hole is almost round then you may not be able to get enough grip whatever you do. So one answer is to very carefully araldite the tightest allen key you can get in. If this doesn`t work then it is possible to dissolve the offending screw in acid. Preferably concentrated nitric acid. You can only do this if there is no brass insert in the knob and the knob is bakelite or ebonite. Failing that make a small trepanning tool from a piece of steel tube about an inch longer than the depth of the screw. (A spacer will do) that will just go over the size of screw you want to remove and has a thin wall. This is done by cutting a few small teeth (say 6 spaced around), like on a saw, on the rim of the tube. Drill a small hole across the other end of the tube to put a small tommy bar in. Drill carefully the hole in the knob to the outside diameter of the tool and then use the tool to drill out around the offending screw. You can then retap the hole with the next size up.

Pat G3IKR

Brian R Pateman · 1st Jul 2009, 5:56 am

This has been covered before. There is a lengthy thread here;

https://www.vintage-radio.net/forum/...ight=grubscrew

which details various methods.

'LIVEWIRE?' · 14th Jul 2009, 10:45 am

I have a similar problem where th knob ON the tuning shaft of a Ferranti U1016 cannot be removed, because the grub screw cannot be turned. The only thing I can think of is to try and drill out the screw, but how to support the knob & shaft so that it won't rotate whilst I'm drilling I know not. The entire shaft could be removed from the radio, I guess, but that would then mean restringing the drive cord, which I really don't want to do. Any suggestions as to how to solve this problem?

MichaelR · 14th Jul 2009, 11:15 am

As a suggestion could you use small "mole grips" to grasp the knob. Keeping the knob near the bench hold the grips against the bench to keep the knob steady while you drill ( assuming you use a small electric drill). Not very easy to explain what I intend but maybe you will get the idea.

Key to damage limitation is slowly and careful and do not panic

Mike

'LIVEWIRE?' · 14th Jul 2009, 9:32 pm

I hadn't thought of using mole grips, Michael. May give them a try, though.

igranic · 14th Jul 2009, 10:49 pm

Here is a method that has worked for me.

Clean the grub screw with IPA or Electroclean to remove any traces of grease.
Mix up a small blob of standard, slow-hardening Araldite (quick-hardening is too soft).
Dip the tip of the allen key in the Araldite - don't overdo it.
Insert key and Araldite into the worn grub screw.
Wedge into position and leave in a warm place to harden for at least 24 hours.
When set hard, the Araldite will take up the wear and should allow the screw to be undone.
If screw is still stubborn, treat the thread with PlusGas or similar penetrating fluid and leave for a further 24 hours before trying again.

Edward

qualityten · 15th Jul 2009, 9:28 pm

I have encountered a further grubscrew/knob problem, namely that after removing the grubscrew, the plastic knob will not shift. I've tried tapping through the hole, or directly on the knob, and loads of WD40, over weeks, but the knob won't shift. I need to remove it to service some resistors behind the front plate and I'm reluctant to break it free as it is an original of a matching set of 5, all in good condition. The other 4 unscrewed and slipped off easily (!).

David

AlanBeckett · 15th Jul 2009, 9:51 pm

David,
Dumb question?
Another grubscrew?
Alan

Herald1360 · 15th Jul 2009, 10:02 pm

WD40 isn't that good as a penetrating oil, it's really just a Water Dispersant. Try "Plus Gas" instead.....

OErjan_S · 15th Jul 2009, 10:09 pm

agree that WD40 is NOT! a penetrating lubricant, even plain old mineral oil is better.

qualityten · 17th Jul 2009, 3:03 pm

Thanks for setting me right about WD40. Will get some decent penetrating oil, as most of the tasks I undertake seem to have at least one seized screw. Was repairing a Thorens TP13 tonearm yesterday with lots of rust damage. The only screws I could not loosen were the bearing ones. (I have worked on these arms before, so know how they come apart.)

David

p.s. What is Plus Gas?

M0TGX Terry · 17th Jul 2009, 5:30 pm

Plus Gas is a very effective penetrating oil. Comes in an aerosol from Halfords. I use it all the time on my vintage Morgan.
Regards
Terry

qualityten · 17th Jul 2009, 8:15 pm

Thanks Terry. Picked up a can today and it's hopefully working wonders as I type.

By the way, the motor factors also had cans of a new penetrating spray that first freezes seized parts at minus 48C and then delivers penetrating oil. But I decided to go with the recommendation here.

David

qualityten · 17th Jul 2009, 8:17 pm

Re Alan's question: I did try reinserting the screw and tightening it hard to try and loosen the knob's grip on the shaft, but it had no effect.
David

Neil Purling · 18th Jul 2009, 8:59 pm

Here is the situation I have a radio before me.......
It has not been out of it's case in a very long time & has been left in a loft/garage for a extremely long time.
How can I be reasonably sure of getting all the knobs off intact?
Do you drip a proprietary freeing oil onto the grub screw?
What works best?

Save me from having to ask about a duplicate knob, please.

benjamin77 · 18th Jul 2009, 9:42 pm

Hi Neil. I came accross the same problem just recently

Try using some WD40 in the grub screw hole. 3in1 is 2 thick and is a lubricant not a penetrating oil. Do this over a couple of days then try applying some heat from a hair dryer.

This should shift them

AlanBeckett · 18th Jul 2009, 10:08 pm

There's a current Thread about this - https://www.vintage-radio.net/forum/...ad.php?t=42575 - which also quotes older Threads.
Alan

igranic · 18th Jul 2009, 10:26 pm

I think you will find that Plus Gas, available in aerosol or spout-can, is a far better penetrating fluid. WD40 is primarily a water dispersant.
See this thread.

Successful knob removal requires different techniques dependent upon the type of knob and the cabinet configuration. The make and model of the radio and, even better, a close-up picture or two, would be useful.

Edward

30th Jun 2009, 9:20 pm	#1
MichaelR Retired Dormant Member Join Date: Mar 2006 Location: Sheffield, South Yorkshire, UK. Posts: 1,587	Grubscrew removal Hi to those "in the know", Could anybody offer Tips or hints as to how to remove grubscews that have been worn so that suitable allen keys cannot be used to turn them. regards Mike

30th Jun 2009, 9:33 pm	#2
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Grubscrew removal Mike, I've done the following, although it's a bit SorB:- Choose the next size up - metric if the original is imperial, and vice versa. Cut off a section of the key so you have a straight piece of hex. Support the knob or whatever, line up the flats on the hex with the flats on the corpse as best you can and tap it in, hard. Unscrew it. I've tried it with brass rod filed up but it's not hard enough. The ball-ended keys are best, but more expensive. The secret is a good tight fit and hope. I assume you've already applied WD, heat etc. Good luck. Alan

30th Jun 2009, 11:53 pm	#3
Oldtimer74 Rest in Peace Join Date: Apr 2008 Location: Worcester, Worcestershire, UK. Posts: 330	Re: Grubscrew removal I assume you are talking about grub screws in knobs. If they are so worn that the hole is almost round then you may not be able to get enough grip whatever you do. So one answer is to very carefully araldite the tightest allen key you can get in. If this doesn`t work then it is possible to dissolve the offending screw in acid. Preferably concentrated nitric acid. You can only do this if there is no brass insert in the knob and the knob is bakelite or ebonite. Failing that make a small trepanning tool from a piece of steel tube about an inch longer than the depth of the screw. (A spacer will do) that will just go over the size of screw you want to remove and has a thin wall. This is done by cutting a few small teeth (say 6 spaced around), like on a saw, on the rim of the tube. Drill a small hole across the other end of the tube to put a small tommy bar in. Drill carefully the hole in the knob to the outside diameter of the tool and then use the tool to drill out around the offending screw. You can then retap the hole with the next size up. Pat G3IKR

1st Jul 2009, 5:56 am	#4
Brian R Pateman Nonode Join Date: Jun 2005 Location: Western Lake District, Cumbria (CA20) - UK Posts: 2,136	Re: Grubscrew removal This has been covered before. There is a lengthy thread here; https://www.vintage-radio.net/forum/...ight=grubscrew which details various methods. __________________ Brian

14th Jul 2009, 10:45 am	#5
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Grubscrew removal I have a similar problem where th knob ON the tuning shaft of a Ferranti U1016 cannot be removed, because the grub screw cannot be turned. The only thing I can think of is to try and drill out the screw, but how to support the knob & shaft so that it won't rotate whilst I'm drilling I know not. The entire shaft could be removed from the radio, I guess, but that would then mean restringing the drive cord, which I really don't want to do. Any suggestions as to how to solve this problem?

14th Jul 2009, 11:15 am	#6
MichaelR Retired Dormant Member Join Date: Mar 2006 Location: Sheffield, South Yorkshire, UK. Posts: 1,587	Re: Grubscrew removal As a suggestion could you use small "mole grips" to grasp the knob. Keeping the knob near the bench hold the grips against the bench to keep the knob steady while you drill ( assuming you use a small electric drill). Not very easy to explain what I intend but maybe you will get the idea. Key to damage limitation is slowly and careful and do not panic Mike Last edited by MichaelR; 14th Jul 2009 at 11:15 am. Reason: spelling

14th Jul 2009, 9:32 pm	#7
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Grubscrew removal I hadn't thought of using mole grips, Michael. May give them a try, though.

14th Jul 2009, 10:49 pm	#8
igranic Rest in Peace Join Date: Jan 2005 Location: North Bedfordshire, UK. Posts: 395	Re: Grubscrew removal Here is a method that has worked for me. Clean the grub screw with IPA or Electroclean to remove any traces of grease. Mix up a small blob of standard, slow-hardening Araldite (quick-hardening is too soft). Dip the tip of the allen key in the Araldite - don't overdo it. Insert key and Araldite into the worn grub screw. Wedge into position and leave in a warm place to harden for at least 24 hours. When set hard, the Araldite will take up the wear and should allow the screw to be undone. If screw is still stubborn, treat the thread with PlusGas or similar penetrating fluid and leave for a further 24 hours before trying again. Edward

15th Jul 2009, 9:28 pm	#9
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,312	Re: Grubscrew removal I have encountered a further grubscrew/knob problem, namely that after removing the grubscrew, the plastic knob will not shift. I've tried tapping through the hole, or directly on the knob, and loads of WD40, over weeks, but the knob won't shift. I need to remove it to service some resistors behind the front plate and I'm reluctant to break it free as it is an original of a matching set of 5, all in good condition. The other 4 unscrewed and slipped off easily (!). David

15th Jul 2009, 9:51 pm	#10
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Grubscrew removal David, Dumb question? Another grubscrew? Alan

15th Jul 2009, 10:02 pm	#11
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Grubscrew removal WD40 isn't that good as a penetrating oil, it's really just a Water Dispersant. Try "Plus Gas" instead.....

15th Jul 2009, 10:09 pm	#12
OErjan_S Retired Dormant Member Join Date: Mar 2007 Location: Skelleftea, Sweden Posts: 250	Re: Grubscrew removal agree that WD40 is NOT! a penetrating lubricant, even plain old mineral oil is better.

17th Jul 2009, 3:03 pm	#13
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,312	Re: Grubscrew removal Thanks for setting me right about WD40. Will get some decent penetrating oil, as most of the tasks I undertake seem to have at least one seized screw. Was repairing a Thorens TP13 tonearm yesterday with lots of rust damage. The only screws I could not loosen were the bearing ones. (I have worked on these arms before, so know how they come apart.) David p.s. What is Plus Gas?

17th Jul 2009, 5:30 pm	#14
M0TGX Terry Hexode Join Date: Sep 2005 Location: Grantham, Lincolnshire, UK. Posts: 262	Re: Grubscrew removal Plus Gas is a very effective penetrating oil. Comes in an aerosol from Halfords. I use it all the time on my vintage Morgan. Regards Terry __________________ Terry the Morganist

17th Jul 2009, 8:15 pm	#15
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,312	Re: Grubscrew removal Thanks Terry. Picked up a can today and it's hopefully working wonders as I type. By the way, the motor factors also had cans of a new penetrating spray that first freezes seized parts at minus 48C and then delivers penetrating oil. But I decided to go with the recommendation here. David

17th Jul 2009, 8:17 pm	#16
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,312	Re: Grubscrew removal Re Alan's question: I did try reinserting the screw and tightening it hard to try and loosen the knob's grip on the shaft, but it had no effect. David

18th Jul 2009, 8:59 pm	#17
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Removal of radio knobs Here is the situation I have a radio before me....... It has not been out of it's case in a very long time & has been left in a loft/garage for a extremely long time. How can I be reasonably sure of getting all the knobs off intact? Do you drip a proprietary freeing oil onto the grub screw? What works best? Save me from having to ask about a duplicate knob, please.

18th Jul 2009, 9:42 pm	#18
benjamin77 Retired Dormant Member Join Date: May 2009 Location: High Wycombe, Buckinghamshire, UK. Posts: 326	Re: Removal of radio knobs Hi Neil. I came accross the same problem just recently Try using some WD40 in the grub screw hole. 3in1 is 2 thick and is a lubricant not a penetrating oil. Do this over a couple of days then try applying some heat from a hair dryer. This should shift them

18th Jul 2009, 10:08 pm	#19
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Removal of radio knobs There's a current Thread about this - https://www.vintage-radio.net/forum/...ad.php?t=42575 - which also quotes older Threads. Alan

18th Jul 2009, 10:26 pm	#20
igranic Rest in Peace Join Date: Jan 2005 Location: North Bedfordshire, UK. Posts: 395	Re: Removal of radio knobs I think you will find that Plus Gas, available in aerosol or spout-can, is a far better penetrating fluid. WD40 is primarily a water dispersant. See this thread. Successful knob removal requires different techniques dependent upon the type of knob and the cabinet configuration. The make and model of the radio and, even better, a close-up picture or two, would be useful. Edward